The exemplary embodiments generally relate to media handling and finishing for machines, such as printers and copiers for producing documents, booklets and other materials and specifically relate to booklet makers.
Folding or creasing a stack of several sheets of paper in the middle of the paper is part of forming a booklet. The sheets may be stapled at the fold line, resulting in a stapled booklet or bound in some other manner. A booklet is formed in a booklet maker, where a crease blade strikes the middle of the stack and pushes the stack towards a pair of nipped (upper and lower) crease rolls, which are typically made of an elastomer material. The blade stops at a fixed distance before the centerline of crease rolls. The crease blade does not travel through the crease rolls. The distance between the tip of the crease blade and the centerline of the crease rolls is important to the function of the booklet maker. If the crease blade is pushed too far into the crease rolls, sheet wrinkling or blade/roll jamming may occur. If the crease blade stops too far away from the crease rolls and the sheets are slippery, the sheet(s) closest to the crease rolls may be pulled off the stack of paper. Sheets may be slippery for many reasons, such as the media type, waxy toners, color ink, area coverage, and the like. The sheet closest to the crease rolls that is pulled off the stack is often the cover of the booklet. If the booklet is stapled, the cover sheet (and possibly more sheets) may be torn off the stapled portion, resulting in a paper jam and or a damaged document.
This problem has previously been tackled by allowing the crease blade to travel through the crease rolls, by protruding segments past the blade tip and segmenting the crease rolls. The blade segments travel between and through the roll segments, thereby pushing the sheets through the rolls. Because of the segmented characteristics of the blade and rolls, the roll never pinches the blade and sheet wrinkling or blade or roll jamming cannot occur. In addition, as the blade pushes and forces the sheets through the rolls, the cover sheet does not tear or pull off the stack of paper. This is generally accomplished with two sets of crease rolls. The first is the segmented set, which does not provide a continuous and crisp fold, and its function is to acquire the stack and make the initial crease without allowing the outer sheet(s) to separate from the rest of the book. The second set of rolls is continuous and is used to create the final crisp fold along the entire edge of the book.